U Pegasi

Not to be confused with Upsilon Pegasi.
U Pegasi

A visual band light curve for U Pegasi, plotted from data published by Zhai et al. (1984)[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus[2]
Right ascension 23h 57m 58.477s[3]
Declination +15° 57′ 10.09″[3]
Apparent magnitude (V) 9.23
Min I: 10.07
Min II: 9.73[4]
Characteristics
Evolutionary stage main sequence[5]
Spectral type G2 V + G2: V:[5]
B−V color index 0.648±0.033[2]
Variable type W UMa[6]
Astrometry
Radial velocity (Rv)−28.5±4.7[4] km/s
Proper motion (μ) RA: 34.598 mas/yr[3]
Dec.: 17.389 mas/yr[3]
Parallax (π)5.4708 ± 0.0193 mas[3]
Distance596 ± 2 ly
(182.8 ± 0.6 pc)
Absolute magnitude (MV)3.88[2]
Orbit[5]
Period (P)8.995 h
Eccentricity (e)0 (assumed)
Inclination (i)76.1[7]°
Semi-amplitude (K1)
(primary)		77.6±1.1 km/s
Semi-amplitude (K2)
(secondary)		246.5±1.4 km/s
Details
Primary
Mass1.224±0.003[8] M☉
Radius1.149±0.009[8] R☉
Luminosity1.29[7] L☉
Surface gravity (log g)4.32[8] cgs
Temperature5,860[8] (polar) K
Secondary
Mass0.379±0.002[8] M☉
Radius0.744±0.002[8] R☉
Luminosity0.55[7] L☉
Surface gravity (log g)4.27[8] cgs
Temperature5,785±7[8] (polar) K
Other designations
U Peg, BD+15° 4915, HIP 118149, SAO 108933, PPM 143009, WDS J23579+1557A[9]
Database references
SIMBADdata

U Pegasi is a binary star system in the constellation of Pegasus, abbreviated U Peg. The pair form an eclipsing binary with a combined peak apparent visual magnitude of 9.23,[4] which is far too faint to be visible to the naked eye. During the primary eclipse the magnitude decreases to 10.07, while the secondary eclipse only drops to magnitude 9.73.[4] This system is located at a distance of approximately 596 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of around −28.5 km/s.[4]

The variable luminosity of this system was discovered by S. C. Chandler in 1895. He found it to have a continuously varying light curve with a period of 5.192 h.[10] Observing the star photometrically, in 1898 E. C. Pickering and O. Wendell determined a longer period of 8.995 h.[11] H. Shapley published orbital measures for this eclipsing binary in 1913, estimating their relative luminosities and radii.[12] It was determined to be a variable of the W Ursae Majoris type,[13] and in 1945 the orbital period was shown to vary over time.[14]

  1. ^ Cite error: The named reference Zhai_1984 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  4. ^ a b c d e Cite error: The named reference Gontcharov_2006 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Lu_1985 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference Latković_et_al_2021 was invoked but never defined (see the help page).
  8. ^ a b c d e f g h Cite error: The named reference Pribulla_Vanko_2002 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Chandler_1895 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Pickering_Wendell_1898 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Shapley_1913 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Schilt_1927 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Recillas_Jones_Woodward_1945 was invoked but never defined (see the help page).